1. Field of the Invention
The present invention relates to theatre lighting, and more particularly to a method and apparatus for generating a flash or series of flashes from a multiparameter light.
2. Description of Related Art
Theatre lighting devices are useful for many dramatic and entertainment purposes such as, for example, Broadway shows, television programs, rock concerts, restaurants, nightclubs, theme parks, the architectural lighting of restaurants and buildings, and other events. A multiparameter light is a theatre lighting device that includes a light source and one or more effects known as xe2x80x9cparametersxe2x80x9d that are controllable typically from a remotely located console, which is also referred to as a central controller or central control system. For example, U.S. Pat. No. 4,392,187 issued Jul. 5, 1983 to Bornhorst and entitled xe2x80x9cComputer controlled lighting system having automatically variable position, color, intensity and beam divergencexe2x80x9d describes multiparameter lights and a console. Multiparameter lights typically offer several variable parameters such as strobe, pan, tilt, color, pattern, iris and focus. See, for example, the High End Systems Product Line 2000 Catalog, which is available from High End Systems Inc. of Austin, Tex. The variable parameters typically are varied by optical and mechanical systems driven by microprocessor-controlled motors located inside the housing of the multiparameter light.
A stroboscopic effect is a number of high-intensity short-duration light pulses, which are commonly known as flashes. In conventional multiparameter lights, the strobe parameter is a stroboscopic effect realized with set of algorithms optimized to create a standard best quality stroboscopic effect using the mechanical shutter. The algorithms are stored in a memory of the multiparameter light and are evoked by control values from the remote console over a strobe or shutter control channel. However, other stroboscopic effects may be realized with different algorithms that do not necessarily create the standard stroboscopic effect. For instance, a random strobe with varying dark periods is another type of stroboscopic effect available over the strobe control channel. Other stroboscopic effects may also be available to be controlled over the strobe control channel, such as, for example, slow ramp up and fast ramp down strobes. These different stroboscopic effects typically are all controllable from the strobe control channel and make available more variants for the programmer of the lights.
Multiparameter lights typically use high intensity light sources such as metal halide lamps. A metal halide lamp typically requires a high voltage ignition system to xe2x80x9cstrikexe2x80x9d the lamp into operation. The high voltage ignition system provides the high voltage required by the lamp to carry an electric current between the electrodes. Once current flow is established between the electrodes of the lamp, an operating supply voltage that is typically much lower than the striking voltage is employed to continuously operate the lamp.
If a lamp is shut off, the procedure of applying the striking voltage to the lamp to re-ignite the lamp must be repeated. If one desires to re-ignite a lamp that is warm from operating, the striking voltage needed is higher than the striking voltage needed to re-ignite a cold lamp. This is because as the lamp heats up during operation, the impedance between the electrodes rises. As the lamp cools down, the required striking voltage is reduced.
Because metal halide lamps require high voltage ignition systems and the voltage requirement for the ignition increased with lamp temperature, they cannot be switched off and on rapidly and continuously without considerable expense. Hence, multiparameter lights typically implement the stroboscope parameter by using mechanical shutters.
A mechanical shutter works by controllably blocking and unblocking the light beam from the lamp within the multiparameter light. The mechanical shutter may be formed of a metal such as aluminum, mirrored glass, or steel, and may be driven by a motor or an actuator such as a solenoid. When the mechanical shutter is placed by the motor to block the light beam, very little light exits the multiparameter light. When the mechanical shutter is placed to avoid blocking the light beam, i.e. when it is open, the path of the light through the shutter is clear and the full intensity of the light beam exits the multiparameter light.
More recently, alternatives to mechanical shutters have become available. Generally, a shutter may be any suitable means to block and not block (i.e. open) the light from the light beam created by the lamp, including electronic shutters that become more reflective and less reflective such as some LCDs and that redirect light such as DMDs and some LCDs.
While mechanical shutters are effective for a variety of stroboscopic effects, their usefulness is limited because the strobe contrast declines with an increasing strobe rate. Mechanical shutters are most often driven by motors that are controlled by a microprocessor-based control system located in the multiparameter light housing. The speed of the mechanical shutters is limited by the weight of the shutter itself and the capability of the motor driving the shutter. Mechanical shutters operate reasonably well and provide reasonable strobe contrast at low to moderate strobe rates such as, for example, one flash per second. However, the strobe contrast is reduced at higher strobe rates such as, for example, about ten flashes per second. Reduction in the strobe contrast occurs when the shutter cannot move fast enough to effectively block and unblock the light beam. At ten flashes per second, a mechanical shutter typically provides a poor contrast between the light duration and the dark duration. At greater shutter speeds, the contrast suffers so greatly that the stroboscopic effect produced by the multiparameter light is ineffective.
Illustrative shutter systems in common use are shown in FIGS. 1-7. FIGS. 1-4 illustrate the mechanical action of one kind of shutter system commonly used for the stroboscope in the multiparameter light. Shown is a motor 2, a motor shaft 4, a wedge shaped shutter 6, and a light beam 9 as illustrated by a circular dotted line. Also shown is an aperture 8 through the shutter 6, for passing the light from the light beam unobstructed. In FIG. 1, the shutter 6 is in a light sustaining position, having placed the aperture 8 in coincidence with the light beam 9 as it moves at maximum velocity from top to bottom as shown by the long curved arrow. Next as shown in FIG. 2, the shutter 6 is in one darkness sustaining position, having moved the aperture 8 away from the light beam 9 while in the process of reversing direction. Next as shown in FIG. 3, the shutter 6 is in a light sustaining position, having placed the aperture 8 in coincidence with the light beam 9 as it moves at maximum velocity from bottom to top as shown by the long curved arrow. Next as shown in FIG. 4, the shutter 6 is in another darkness sustaining position, having moved the aperture 8 away from the light beam 9 while in the process of reversing direction. Next, the shutter 6 returns to a light sustaining position identical to the position shown in FIG. 1. FIG. 6 illustrates another type of shutter system. Shown is a motor 12, a motor shaft 14, a shutter 16, and a light beam 19 as illustrated by the dotted circle. A large curve arrow indicates the direction of movement of the shutter 16. FIG. 7 illustrates another type of shutter system using two motors 22 and 32 and respective shutters 26 and 36 which are attached to motor shafts 24 and 34. Large curved arrows indicate the direction of movement of the shutters 26 and 36 relative to a light beam 29, which is illustrated by a dotted circle.
Electronic stroboscopic effects have been achieved using Xenon lamps in high power lighting devices other than multiparameter lights; see, e.g., Easy(trademark) model 2000/2500/3000 outdoor xenon searchlight, which is available from Space Cannon Illumination Inc. of Edmonton, Alberta, Canada. However, xenon lamps are much easier to cause to strobe than the metal halide lamps commonly found in multiparameter lights.
Generally, Xenon lamps do not require a warm up time after they are ignited by a high voltage ignition current. Repeated striking or energizing of a Xenon lamp to produce a stroboscope is quite possible as Xenon lamps do not require a warm up time and instantaneously produce high contrast ratios when used to create a stroboscope. Compact metal halide lamps like those commonly used with multiparameter lighting devices and mercury vapor lamps require warm up times where the metal contained within the arc tube is vaporized.
Multiparameter lights are controlled by a remote console operating in conjunction with a communications system. Most often the communications system protocol used is the DMX standard developed by the United States Institute of Theatre Technology (xe2x80x9cUSITTxe2x80x9d). Basically, the DMX512 protocol requires a continuous stream of data at 250 Kbaud which is communicated one-way from the remote console to the theatre devices. Typically, the theater devices use an Electronics Industry Association (xe2x80x9cEIAxe2x80x9d) standard for multi-point communications know as RS-485. The DMX 512 standard supports up to 512 channels of control. Multiparameter lights having parameters such as pan, tilt, strobe, dimming, color change, focus, zoom, pattern, and iris may often require up to 20 separate channels of control. Typically multiparameter lighting systems may employ over 20 multiparameter lights. In a multiparameter lighting system using the DMX 512 standard with each light requiring up to 20 channels of control, all of the 512 channels available may easily be used. This means that it is an advantage to maintain the number of channels required to operate the multiparameter light at a minimum.
Accordingly, a need exists for multiparameter lights that can achieve good strobe contrast at fast strobe rates. A need also exists for improving strobe contrast even at low to moderate strobe rates. A need also exists for operating multiparameter lights having enhanced strobe capabilities without increasing the number of channels required for control thereof.
It is an object of at least some of the embodiments of the invention to provide an improved stroboscope for a multiparameter light, the improved stroboscope having both a mechanical strobe and an electronic strobe as well as coordinated operation thereof to achieve improved and additional stroboscopic effects.
It is an object of at least some of the embodiments of the invention to provide for control of an improved stroboscope having mechanical and electronic strobes over a single control channel.
It is an object of at least some of the embodiments of the invention to provide for coordinated operation of mechanical and electronic strobes in a multiparameter light.
It is an object of at least some of the embodiments of the invention to maintain the average operating power level of the lamp of a multiparameter light at no more than about the maximum rated power level of the lamp for any particular strobe rate, even while operating the lamp during one or more flashes at greater than the maximum rated power level.
It is an object of at least some of the embodiments of the invention to maintain the average operating power level of the lamp of a multiparameter light at no less than about the minimum rated power level of the lamp for any particular strobe rate, even while operating the lamp between flashes at less than the minimum rated power level.
Some or all of these and other objects and advantages are realized in the various embodiments of the invention. One such embodiment is a method of operating a multiparameter light having a control system, a shutter and an arc lamp to obtain a stroboscopic effect. The method comprises operating the shutter over a first plurality of cycles to obtain flashes at a first frequency, under control of the control system in response to a command signal; and applying a first operating power and a second operating power alternately to the arc lamp over a second plurality of cycles to obtain flashes at a second frequency, under control of the control system in response to a command signal.
Another such embodiment is a method of operating a multiparameter light to obtain a stroboscopic effect, the multiparameter light having a shutter and a mercury-filled lamp powered by a variable power supply, and the mercury-filled lamp having a maximum rated power level and a minimum rated power level. The method comprises determining a high operating power for the mercury-filled lamp; determining a low operating power for the mercury-filled lamp; determining a first duration over which to apply the high operating power to the mercury-filled lamp; determining a second duration over which to apply low high operating power to the mercury-filled lamp; and alternately applying the high operating power for the first duration and the low operating power for the second duration to the mercury-filled lamp over a plurality of cycles to obtain flashes having a desired frequency and duration, wherein the shutter is open for at least a portion of each of the flashes. The high operating power determining step, the low operating power determining step, the first duration determining step, and the second duration determining step result in an average power during the applying step of between about the maximum rated power level and about the minimum rated power level of the mercury-filled lamp.
Another such embodiment is a multiparameter light comprising an arc lamp; a variable power supply coupled to the arc lamp; a shutter; and a control system having an output coupled to the shutter for operating the shutter to obtain a stroboscopic effect, and an output coupled to the variable power supply for operating the arc lamp to obtain a stroboscopic effect.
Yet another such embodiment is a multiparameter light comprising a shutter; an arc lamp; a variable power supply coupled to the arc lamp; and a control system having an output coupled to the variable power supply for operating the arc lamp to obtain a series of flashes, and an output coupled to the shutter for opening the shutter for at least a portion of each of the flashes.
A further such embodiment is a method of operating a multiparameter light, the multiparameter light including at least an arc lamp having a maximum rated power level, a shutter, and a control system. The method comprises applying operating power to the arc lamp less than the maximum rated power level; generating with the control system in response to a command signal a plurality of lamp power control signals; and after the step of applying operating power to the arc lamp less than the maximum rated power level and in response to the lamp power control signals, applying operating power to the arc lamp greater than the maximum rated power level over a first duration and less than the maximum rated power level over a second duration to generate a flash.
Another such embodiment is a method of operating a multiparameter light having at least a shutter and an arc lamp having a maximum rated power level. The method comprises applying operating power to the arc lamp less than the maximum rated power level; after the step of applying operating power to the arc lamp less than the maximum rated power level, applying operating power to the arc lamp greater than the maximum rated power level over a first duration and less than the maximum rated power level over a second duration to generate a flash; and operating the shutter in coordination with the step of applying operating power to generate the flash.
A further such embodiment is a method of operating a multiparameter light, the multiparameter light having a shutter and a mercury-filled lamp powered by a variable power supply, and the mercury-filled lamp having a maximum rated power level and a minimum rated power level. The method comprises determining a high operating power for the mercury-filled lamp greater than the maximum rated power level; determining a low operating power for the mercury-filled lamp less than the minimum rated power; applying various operating powers, including the high operating power and the low operating power, over various time intervals to the mercury-filled lamp to obtain a plurality of flashes; and determining an average power of the various operating powers applied over the various time intervals to the mercury-filled lamp in the applying step; wherein the high operating power determining step and the low operating power determining step are based on maintaining the average power not greater than about the maximum rated power level, and on maintaining the average power not less than about the minimum rated power level.
Yet another such embodiment is a multiparameter light comprising a shutter; a mercury-filled lamp; a variable power supply coupled to the mercury-filled lamp; and a control system having an output coupled to the variable power supply for operating the mercury-filled lamp at various power levels over various durations to obtain flashes of varying duration and intensity and to obtain dark intervals of varying duration and intensity between the flashes, and an output coupled to the shutter for opening the shutter for at least a portion of each of the flashes.